This invention relates generally to high-precision wideband amplifiers, and more particularly to an overdrive thermal compensation mechanism for a cascode feed-forward amplifier.
The cascode feed-forward amplifier taught by Quinn in U.S. Pat. No. 4,146,844 and gaining rapid commercial acceptance as the Quinn "cascomp" amplifier provides vastly improved performance over previous amplifier designs. The Quinn cascomp amplifier employs a correction channel which senses pn junction distortion of a main channel and injects an error-correction signal into a pair of output nodes. The cascomp amplifier when properly biased will compensate for thermal junction-voltage (V.sub.be) in the main channel input devices when presented with a pure differential signal, but cannot maintain this compensation when overdriven, or presented with signals having a common-mode component.